Waste body fluids flow from the kidney through the ureter to the bladder. The fluids pass from the bladder through the urethra to exit a person's body. A blockage occasionally forms in the ureter of some people. The blockage is usually comprised of a hard stone-like material called calculus. Such a blockage can be painful and dangerous since it restricts the flow of waste fluids through the ureter. Ureteral calculus, more commonly known as a kidney stone, may be removed surgically. It is preferable, however, to try to capture the stone and pull it through the ureter, baldder and urethra. Devices and procedures for such capture and removal are, thus, known.
The most common stone retriever device is made from a cable having a wire basket at one end of the cable with a relatively short, somewhat flexible, rod-like end member, called a filiform, at the end of the basket opposite the cable. The basket is usually made of four equally spaced-apart wires which are sufficiently rigid to hold a large V-shape. The filiform of the device is inserted into the ureter and worked past the stone. As the basket is maneuvered alongside the stone, the stone moves into the space surrounded by the wires and is hopefully captured for removal on removal of the cable and basket. The problem with this device is that it is extremely difficult to work the basket around or even with the stone in order to capture the stone. Consequently, the removal procedure may be time consuming and is prone to failure.
Another known device includes a six wire cable having a filiform at the end. The cable is received in a tube. A handle moves the tube about one inch in either direction along the cable. When the tube is retracted, a portion of the cable is exposed, and the wires are preformed and yieldably flexible to expand into a basket shape. This device is used similarly to the previously described device, except the basket is enclosed in the tube and, therefore, is easily moved past the stone once the filiform is worked past the stone. The problem with this device, however, is that the wires of the cable are necessarily thin and flexible and, consequently, when the basket is pulled back past the stone, the wires too often simply collapse and do not capture or dislodge the stone.
Consequently, present stone retrievers are successful in some cases and not successful in far too many. Widespread use of this type of procedure, therefore, probably depends upon the identification of an improved surgical tool.